Ozonation By-products Research Articles

Treatment and degradability of direct dyes in textile wastewater by ozonation: A laboratory investigation

In this study the factors affecting the rate of chemical oxygen demand of a synthetic waste solution containing water soluble direct dyes (Sirius Red F3B and Sirius Blue SBRR) by ozone gas were investigated. The research was conducted using a batch bubble column to take the advantage of the intensive back-mixing that prevails in bubble columns. In result of our experimental study, we have shown that the COD of direct dyestuff wastewater was reduced 58.89% for Sirius Red F3B and 60.95% for Sirius Blue SBRR after ozone bubbling treatment for 2 h. In addition the results indicate that during the ozonation, even though complete Sirius Red F3B and Sirius Blue SBRR degradation occurs in 10 min, ozone consumption goes on for a further 20 min after which time most degradation reactions are completed. Results of kinetic study showed that ozonation of the aqueous direct dyes were a pseudo-first-order reaction with respect to the dye. The apparent rate constant increased with both applied ozone dose and temperature, but declined logarithmically with the initial dye concentration. The main ozonation by-products, identified by HPLC, IC and GC-MS are formaldehyde, acetaldehyde, glyoxal, acetone, acetic acid, formic acid, oxalic acid and carbonic acid, plus nine Sirius Red F3B and twelve Sirius Blue SBRR derivatives are scarcely degradable.

Applying Surrogates and Indicators to Assess Removal Efficiency of Trace Organic Chemicals during Chemical Oxidation of Wastewaters

To respond to concerns associated with wastewater-derived contaminants water utilities are looking for new approaches for monitoring trace organic chemicals in conventional and advanced water treatment processes. This study examines the use of a combination of surrogate parameters and indicator compounds tailored to monitor the removal efficiency of advanced oxidation processes employed by treatment plants engaged in indirect potable water reuse programs. Potential surrogate parameters and indicator compounds, identified by reviewing previous publications and classified by their structural properties, were tested in pilot- and full-scale treatment systems. Dilantin, DEET, meprobamate, and iopromide are good indicators to assess optimized oxidation conditions while ozonating tertiary-treated wastewaters. UVA reduction, ozone byproduct formation, such as simple organic acids, and ozone exposure correlated with "sweet spot" compounds, where ozone exposure correlated with trace organic removal across five tertiary-treated wastewaters. Findings indicate that the proposed framework can serve as a conservative monitoring approach for advanced oxidation processes as well as other indirect potable reuse processes to ensure proper removal of identified and unidentified wastewater-derived organic contaminants, to detect failures in system performance, and is protective of public health.

Aqueous Ethanol modified Nanoscale Zerovalent Iron in Bromate Reduction: Synthesis, Characterization, and Reactivity

Nanoscale zerovalent iron (NZVI) was evaluated for the reduction of bromate that is a highly persistent and carcinogenic oxyhalid formed as an ozonation byproduct during oxidative disinfection in drinking water treatment Solid-phase NZVI with different surface areas was controllably synthesized using a liquid phase reduction. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and a Brunauer-Emmett-Teller (BET) surface area and porosity analyzer were utilized to characterize particle size, surface morphology, surface area, and corrosion layers formed onto NZVI before and afterthe reduction of bromate. Surface area of synthesized NZVI was found to be influenced strongly by ethanol contents during synthesis with a maximum surface area of 67.51 +/- 0.35 m2/g in a 90% aqueous ethanol; additionally, capsule structures of NZVI with amorphous phase, in which tens of particles with diameters of 2-5 nm were packed into an iron oxide/hydroxide layer, were also synthesized using 100% ethanol as a solvent. Subsequent XRD and TEM results revealed that in a 20 min bromate reduction NZVI mostly converted to Fe2O3 and Fe3O4 corrosion products mixed with iron hydroxides. Compared to bromate reduction using microsized ZVI in a pseudo-first-order kinetic model, NZVI enhanced the reduction efficiency following a second-order kinetic model, with observed second-order rate constants (kobs) of 2.57 x 10(-4) to 2.19 x 10(-3) microg(-1) min(-1) L. Humic acid was found to be the most influencing factorto decrease NZVI reactivity in bromate reduction. However, the effect of sonication pretreatment showed that the bromate reduction efficiency could be enhanced by increasing the actual reactive surface area. Our results suggest that application of NZVI is a viable process for bromate reduction in water treatment.

Catalytic Ozonation of Toluene Using Zeolite and MCM-41 Materials

The effects of passing ozone over different zeolite and MCM-41 materials to remove toluene were investigated. Different ozone-to-toluene ratios were used to evaluate the catalytic performance during ozonation. The micro- and meso-porous materials removed about 50% of the toluene via adsorption and another 20-40% was decomposed by ozonation, which was catalytically enhanced by the zeolite and MCM-41 materials. The catalytic reaction portion increased by using a higher ozone inlet concentration and it was further enhanced to around 50% with the use of more adsorbents or with longer residence times. Inside the porous structure of the material, ozone was either decomposed into active atomic oxygen for reactions or converted into oxygen for active site regeneration. The number of Lewis acid sites in the adsorbents for ozone decomposition and byproduct generation during the reactions limit the catalytic activities. Trace amounts of intermediates including aldehydes and organic acids were quantified in the ozonation process. A higher ozone inlet concentration helped to reduce intermediate species formation but it led to more residual ozone in the exhaust. The high adsorption capability of the zeolite and MCM-41 adsorbents could serve as reservoirs for suppressing the release of intermediate species to the exhaust.

Disinfection by-product formation and mutagenic assay caused by preozonation of groundwater containing bromide

Brominated organic and inorganic by-products are generated during ozonation of groundwater containing high bromide concentrations. This study measured concentrations of bromate, bromoform, bromoacetic acids, bromoacetonitriles, bromoacetone, 2,4-dibromophenol and aldehyde generated by ozonation. The potential mutagenicity of ozonated waters was assessed using the Ames and Microtox tests. Test results for the 18 ozonated groundwater samples demonstrate that bromate formation is associated with high pH, bromide and alkalinity content, low levels of dissolved organic carbon (DOC) and ammonia, and low alkalinity. Brominated organic by-products were correlated with high bromide ion and natural organic matter content, and low ammonia concentrations. The Ames test results demonstrate that all extracts from ozonated water have mutagenic activity; however, the 18 raw groundwater samples had no mutagenicity. The Microtox test results also show that the ozonated water samples were highly toxic. Generally, both bromide and DOC content promoted the formation of ozonation by-products and mutagenicity. Controlling of bromide and DOC concentrations is an effective method of reducing potential by-product formation and eliminating mutagenicity problems associated with groundwater ozonation.

Effective Ozonation of Secondary Effluents with Initial Ozone Demand

It is clarified that the ozone consumption during the initial stage of ozonation before dissolved ozone appears is the same value as that during the initial 20 seconds in batch mode experiment. This initial ozone consumption was defined as initial ozone demand (IOD) in this study. IOD of secondary effluent was shown to be 0.3–0.5 mgO3/mgC0. More than 90% of 17β-estradiol (E2) was reduced, and formation of ozonation by-products was controlled within this ozone demand. This state can be also characterized by reduction of the values of UV254, fluorescence intensity at 345 nm (Excitation)/435 nm (Emission) and that at 240 nm/435 nm to 0.06 /cm, 35 and 15, respectively.

Removal of pharmaceutical compounds, nitroimidazoles, from waters by using the ozone/carbon system

The main objective of this study was to analyze the effectiveness of technologies based on the use of ozone and activated carbon for the removal of nitroimidazoles from water, considering them as model of pharmaceutical compounds. A study was undertaken of the influence of the different operational variables on the effectiveness of each system studied (O 3, O 3/activated carbon), and on the kinetics involved in each process. Ozone reaction kinetics showed that nitroimidazoles have a low reactivity, with k O 3 values <350 M −1 s −1 regardless of the nitroimidazole and solution pH considered. However, nitroimidazoles have a high affinity for HO radicals, with radical rate constant ( k HO) values of around 10 10 M −1 s −1. Among the nitroimidazole ozonation by-products, nitrate ions and 3-acetyl-2-oxazolidinone were detected. The presence of activated carbon during nitroimidazole ozonation produces (i) an increase in the removal rate, (ii) a reduction in the toxicity of oxidation by-products, and (iii) a reduction in the concentration of dissolved organic matter. These results are explained by the generation of HO radicals at the O 3–activated carbon interface.

Degradation of macromolecular tannic acid by O3/H2O2

Tannic acid, being polyhydroxyl, is a macromolecule natural organic matter. The efficiency and mechanism of degradation of tannic acid by O3 and O3/H2O2 was studied. The results showed that the addition of H2O2 had no obvious improvement on the ozonation efficiency of tannin. It was observed that the addition of H2O2 decreased the removal efficiency of TOC by 10%. The relative intensity of .OH generated in the O3-H2O2 system was detected by electronic spin resonance (ESR) and it was found that tannin consumed the .OH radicals, which may be associated with the polyhydroxyl structure of tannin. Derived with PFBBr and analysed by GC-ECD, the by-products of tannin ozonation were found to be aldehydes such as acetaldehyde, glyoxal and methyl glyoxal. Analysis with an ion chromatogram showed that the final products of tannin were oxalic acid, ketomalonic acid and oxalic acid, which consisted of 35% of TOC in both systems.

Effect of Bromide and Ammonia on the Formation of Ozonation and Chlorination By-Products

The objective of this investigation was performed to assess the effects of bromide and ammonia concentrations on the formation of ozonation and chlorination by-products including bromate, trihalomethanes (THMs), and haloacetic acid (HAAs). The results of this investigation reveal that increasing bromide, ozone dosage, and decreasing ammonia concentrations would enhance the bromate formation. Bromate formation was inhibited by ammonia significantly when the bromide concentration was introduced above 1.0 mg∕L . Moreover, the range of percent of bromide incorporation for bromate was between 1.2 and 2.3%. Bromide would generate more bromide-containing species of THMs and HAAs formation indicating the higher bromine incorporation factor (BIF) value of THMs and HAAs. Ammonia reduced the THMs and HAAs formation obviously, but the effect of ammonia on BIF value is insignificant. Results of the factor analysis suggest that the principle parameters such as ozone, bromide, and reaction time should be utilized for de...

Relationship between Oxidation Products and Estrogenic Activity during Ozonation of 4-Nonylphenol

The ozonation of 4-nonylphenol was investigated in this study. The mixtures of 4-nonylbenzoquinone homologues, 4-nonylcatechol homologues and carboxylic compounds formed during ozonation of 4-nonylphenol, were identified as oxidation by-products by gas chromatography-mass spectrometry. The estrogenic activity of ozonation by-products of 4-nonylphenol was studied using a recombinant yeast bioassay. The mixtures of 4-nonylcatechol homologues have higher estrogenic activity, while mixtures of 4-nonylbenzoquinone homologues have lower estrogenic activity than 4-nonylphenol. However, the estrogenic activity of 4-nonylphenol ozonation solution could be eliminated ultimately. The removal of the estrogenic activity of 4-nonylphenol was enhanced by the addition of humic acid, indicating the favorable effect of the presence of natural organic materials in water treatment.

Experimental Study on Indoor Air Cleaning Technique of Nano-Titania Catalysis Under Plasma Discharge

In this study, a new technique of air cleaning by plasma combined with catalyst was proposed, which consisted of electrostatic precipitation, volatile organic compounds (VOCs) decomposition and sterilization. A novel indoor air purifier based on this technique was adopted. The experimental results showed that formaldehyde decomposition by the plasma-catalyst hybrid system was more efficient than that by plasma only. Positive discharge was better than negative discharge in formaldehyde removal. Meanwhile, the outlet concentration of ozone byproduct was effectively reduced by the nano-titania catalyst.

Ozonation By-products and Determination of Extracellular Release in Freshwater Algae and Cyanobacteria

This work identifies the cyanobacterial and algal extracellular products (ECPs) and their derived byproducts during preozonation. Laboratory experiments were performed on two cyanobacterial species (Oscillatoria tenuisa and Microcystis aeruginosa) and one algal species (Chlorella sp.) dominating eutrophic reservoirs. Gas chromatography, coupled with high-resolution electron-impact mass spectrometry (GC/EI-MS), and high-performance anion-exchange chromatography (HPAEC) was adopted. Over 20 compounds were detected in the mass spectra analyses of the cyanobacterial and algal extracts (including cells and filtrates). The main identified ECPs were classified as monosaccharides, fatty acids, hydrocarbons, and aldehydes. Odor-causing substances were also present in the cyanobacteria, such as trans-1,10-dimethyl-trans-9-decalol (geosmin) and 2-methylisoborneol (2-MIB). The results from ozonated cyanobacteria and algae indicated that the dissolved organic carbon (DOC) content of culture suspensions increased during ozonation. Most of the additional DOC is produced by the increased liberation of ECPs to the bulk phase. Several byproducts were present in the ozonated cyanobacterial and algal cultures: a total of 22 different organic compounds were detected—mostly aldehydes and phthalates.

Are we about to upgrade wastewater treatment for removing organic micropollutants?

Activated sludge treatment allows only for a partial removal of micropollutants, mainly via sorption and biological degradation. Ozonation and activated carbon filtration are processes bearing the potential to drastically reduce the micropollutant load discharged to the environment after (centralized) biological treatment. The estimated total costs between 0.05 and 0.20 euro per m3 treated water (depending on plant size and effluent DOC content) represent only a small fraction of the total costs for urban wastewater management and are therefore considered feasible. Full scale testing is currently planned or under way with the aim to a) confirm this cost estimation and b) to demonstrate the benefit by quantification of the effect of removal and by documenting the impact on the ecology of receiving waters. Ozonation would have the additional advantage of achieving partial disinfection. Another issue currently being intensively studied is the byproducts formed during ozonation and their toxicity. Evidence is needed that the formed ozonation byproducts are either harmless or easily degradable. Since a 5% to 20% loss of sewage is occurring due to sewer leakage and combined sewer overflow an improved reduction of micropollutant input to the aquatic environment requires that advanced centralized treatment is complemented with measures taken before discharge into the sewer. Options hereto may be waste design, labeling of compounds according to environmental friendliness or separate treatment of quantitatively significant point sources (e.g. hospital wastewater, nursery homes, industrial wastewater).

Characterisation of carbonyl byproducts of drinking water ozonation

Ozone treatment of drinking waters has been applied for a range of purposes including taste and odour control, inactivation of protozoan parasites, degradation of cyanotoxins, ‘enhanced coagulation’, ‘enhanced biodegradation’ and oxidative degradation of recalcitrant organics. Molecular ozone reacts at unsaturated sites of natural organic matter (NOM) to produce smaller oxygenated molecules including carbonyl compounds such as aldehydes, ketones, and carboxylic acids. The elucidation of the nature and precise identity of these ozonation by-products is hindered by two complicating factors. The first is the inherent aqueous solubility of many of these compounds, which renders their efficient extraction from water difficult to achieve. Second is the lack of established identity of specific potential by-products, which complicates targeted analytical approaches. To address these challenges, we have approached the task of by-product identification by methods involving aqueous functional group-specific derivatisation reactions. A range of carbonyl byproducts were identified during laboratory-scale testing. These ranged in size from formaldehyde up to 7-carbon species with multiple carbonyl and hydroxyl functional groups.

Ozone consumption and volatile byproduct formation from surface reactions with aircraft cabin materials and clothing fabrics

We measured ozone consumption and byproduct formation on materials commonly found in aircraft cabins at flight-relevant conditions. Two series of small-chamber experiments were conducted, with most runs at low relative humidity (10%) and high air-exchange rate (∼20 h −1). New and used cabin materials (seat fabric, carpet, and plastic) and laundered and worn clothing fabrics (cotton, polyester, and wool) were studied. We measured ozone deposition to many material samples, and we measured ozone uptake and primary and secondary emissions of volatile organic compounds (VOCs) from a subset of samples. Deposition velocities ranged from 0.06 to 0.54 cm s −1. Emissions of VOCs were higher with ozone than without ozone in every case. The most commonly detected secondary emissions were C 1 through C 10 saturated aldehydes and the squalene oxidation products 6-methyl-5-hepten-2-one and acetone. For the compounds measured, summed VOC emission rates in the presence of 55–128 ppb (residual level) ozone ranged from 1.0 to 8.9 μmol h −1 m −2. Total byproduct yield ranged from 0.07 to 0.24 moles of product volatilized per mole of ozone consumed. Results were used to estimate the relative contribution of different materials to ozone deposition and byproduct emissions in a typical aircraft cabin. The dominant contributor to both was clothing fabrics, followed by seat fabric. Results indicate that ozone reactions with surfaces substantially reduce the ozone concentration in the cabin but also generate volatile byproducts of potential concern for the health and comfort of passengers and crew.

N-nitrosodimethylamine (NDMA) formation during ozonation of dimethylamine-containing waters

Ozonation of aqueous solutions of dimethylamine (DMA) leads to the formation of nitrosodimethylamine (NDMA). The yield of reaction is low (below 0.4% in relation to DMA) and increases with increasing pH. Contact time, ozone/DMA ratio and radical scavengers are other variables controlling the yield of reaction. Data from the literature and observed ozonation by-products suggest that nitrosation of DMA might be responsible for nitrosamine generation. NDMA can be recognized as a by-product of ozonation of DMA in water, which is formed in a specific, but reasonable, range of ozone/DMA ratios. The reaction may have potential importance for water treatment technology assuming reasonable micrograms per liter of DMA concentrations in raw waters.

Using EEFM (Excitation Emission Fluorescence Matrix) to Differentiate the Organic Properties of the Effluents from the Ozonated Biofilters

This study conducted a two-stage experiment. The first stage attempted to establish biostable filter beds. Two parameters, total bacterial count (TBC) and non-purgeable dissolved carbon (NPDOC), measured by passing through a 0.2 μm membrane filter, were selected to compare the difference of biostability of a filtration system with recirculation with different O3-to-NPDOC ratios of filtered water. The excitation emission fluorescence matrix (EEFM) was used as an effective tool for understanding information regarding organic characteristics by comparing source filtered water before and after ozonation and the effluent during biostablizing filter. During the second stage, a biostable filter was used to compare differences in biodegradability of ozonated products sodium oxalate and sodium acetate. Experimental results demonstrate that both parameters, NPDOC removal and TBC, can be utilized to evaluate the biostabilty of a filter bed. With each parameter, a plateau was reached in roughly 20 days. The source water from Chen Ching Lake (CCL) contained a protein-like substance determined by the EEFM. This protein-like substance was also destroyed by O3/NPDOC = 1.1. Soluble microbial products (SMPs) released from the biostablizing filter into the effluent have two peaks in the EEFM, identified as protein-like and humic-like acid. The NPDOC removal for the biostabilizing filter using O3/NPDOC = 1.7 was less than that using O3/NPDOC = 1.1. Bacterial counts in the effluent from the biostabilizing filter using O3/NPDOC = 1.1 was better than that of O3/NPDOC = 1.7. This difference can be explained by the high ratio of O3/NPDOC producing by-products of ozonation that were easily utilized by microorganisms; however, filter bed also released relatively more SMPs owing to increased proliferation of microorganisms attached to glass pellets in the filter. Regarding the differences in decomposition of the by-products of ozonation by the biostable filter, such as sodium oxalate, the NPDOC removal at O3/NPDOC = 1.1 was better than that at O3/DOC = 1.7. This phenomenon can be explained as previously mentioned.

Formation and emissions of carbonyls during and following gas-phase ozonation of indoor materials

Ozone concentrations that are several orders of magnitude greater than typical urban ambient concentrations are necessary for gas-phase ozonation of buildings, either for deodorization or for disinfection of biological agents. However, there is currently no published literature on the interaction of building materials and ozone under such extreme conditions. It would be useful to understand, for example in the case of building re-occupation planning, what types and amounts of reaction products may form and persist in a building after ozonation. In this study, 24 materials were exposed to ozone at concentrations of 1000 ppm in the inlet stream of experimental chambers. Fifteen target carbonyls were selected and measured as building ozonation by-products (BOBPs). During the 36 h that include the 16 h ozonation and 20 h persistence phase, the total BOBP mass released from flooring and wall coverings ranged from 1 to 20 mg m −2, with most of the carbonyls being of lower molecular weight (C 1–C 4). In contrast, total BOBP mass released from wood-based products ranged from 20 to 100 mg m −2, with a greater fraction of the BOBPs being heavier carbonyls (C 5–C 9). The total BOBP mass released during an ozonation event is a function of both the total surface area of the material and the BOBP emission rate per unit area of material. Ceiling tile, carpet, office partition, and gypsum wallboard with flat latex paint often have large surface areas in commercial buildings and these same materials exhibited relatively high BOBP releases. The greatest overall BOBP mass releases were observed for three materials that building occupants might have significant contact with: paper, office partition, and medium density fiberboard, e.g., often used in office furniture. These materials also exhibited extended BOBP persistence following ozonation; some BOBPs (e.g., nonanal) persist for months or more at emission rates large enough to result in indoor concentrations that exceed their odor threshold.

Effects of organophosphorus pesticides and their ozonation byproducts on gap junctional intercellular communication in rat liver cell line

The effects of organophosphorus pesticides (OPs), oxons and their ozonation byproducts on gap junctional intercellular communication (GJIC) on cultured BRL cell line were investigated using scrape loading and dye transfer (SL/DT) technique. The neutral red uptake assay was used to identify the non-cytotoxic levels of diazinon, parathion and methyl-parathion applied to GJIC assay. The concentration-dependent inhibition of GJIC was observed over a range of 50–350 mg/l diazinon, parathion and methyl-parathion after 90 min incubation compared with the vehicle control. However, oxons and ozonation byproducts of OPs had no inhibition effect on GJIC at any of the concentrations tested. The inhibition of GJIC by OPs was reversible after removal of the tested pesticides followed by incubation with fresh medium. The present study suggested that the ozonation treatment could be used for the detoxification of drinking water and food crops contaminated with diazinon, parathion and methyl-parathion without formation of GJIC toxicity.

Application of the differential neural network observer to the kinetic parameters identification of the anthracene degradation in contaminated model soil

In this work a new technique dealing with differential neural network observer (DNNO), which is related with differential neural networks (DNN) approach, is applied to estimate the anthracene dynamics decomposition and to identify the kinetic parameters in a contaminated model soil treatment by simple ozonation. To obtain the experimental data set, the model soil (sand) is combined with an initial anthracene concentration of 3.24 mg/g and treated by ozone (with the ozone initial concentration 16 mg/L) during 90 min in a reactor by the “fluid bed” principle. The anthracene degradation degree was controlled by UV–vis spectrophotometry and HPLC techniques. Based on the HPLC data, the obtained results confirm that anthracene may be decomposed completely in the solid phase by simple ozonation during 20 min and by-products of ozonation are started to be destroyed after 30 min of treatment. In the ozonation process the ozone concentration in the gas phase at the reactor outlet is registered by an ozone detector. The variation of this parameter is used to obtain the summary characteristic curve of the anthracene ozonation (ozonogram). Then, using the experimental decomposition dynamics of anthracene and the ozonogram, the proposed DNNO is trained to reconstruct the anthracene decomposition and to estimate the anthracene ozonation constant using the DNN technique and a modified Least Square method.